1. Field of the Invention
The invention relates to a data processing apparatus such as a computer, a printer or other office automation equipment. More particularly, the invention relates to an information processing apparatus having a bidirectional interface capable of transmitting and receiving data.
2. Description of the Related Art
There exist data processing apparatuses such as computers, printers and other office automation equipment having a bidirectional interface capable of transmitting and receiving data illustratively to and from an outside host computer. In operation, the conventional bidirectional interface of the above type of apparatus usually remains in receiving mode ready to receive data, e.g., from the host computer. Where the data processing apparatus is to transmit data through its bidirectional interface to the host computer, the controller of the apparatus first supplies the bidirectional interface with a special control signal. The control signal causes the bidirectional interface to leave receiving mode and enter transmitting mode for data transmission toward the host computer. The controller then starts transmitting data to the host computer via the bidirectional interface. In a bidirectional data communication setup, as outlined, the conventional bidirectional interface has a special control signal supplied thereto in order to change the direction of data transmission and reception before moving the data in the desired direction.
The fact that the conventional data processing apparatus uses the specific control signal to switch the data moving direction requires a signal line (for sending the control signal) and the CPU to provide direction switching control processing. One disadvantage of this requirement is that most conventional data processing apparatuses offer poor responsiveness in switching between the data transmitting and receiving directions. Another disadvantage is that the signal line volume and the control processing overhead tend to increase and get complicated.